Fireplaces

ABSTRACT

A fireplace has an imperforate dished fire-pan, the sloping sides of which support the fire, which radiates through an opening in the wall of a conical enclosure superposed on the fire-pan. An outer frustoconical casing in most cases surrounds the enclosure, with an opening in register with the opening in the disclosure, and defines an air circulation space through which air circulates upwardly from beneath the fire-pan up into the room. A duct from the exterior of the room to be heated may extend into the space beneath the fire-pan, which space may also contain a water pan to humidify the circulating air. A fire control member is rotatable between the enclosure and the casing so as optionally to obturate the openings therein with either a mesh fire screen or a plate closing off the openings. The fireplace aims to provide complete and controllable combustion of wood fuel, and efficient space heating and, optionally, ventilation of a room in which it is situated.

REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of my co-pending applicationSer. No. 549,837, filed Feb. 13, 1976, abandoned.

FIELD OF THE INVENTION

The field of the invention is prefabricated metal fireplaces.

REVIEW OF THE PRIOR ART

Numerous designs of fireplace of essentially sheet metal constructionare known, but all either require to be transferred from the factory tothe user substantially in one piece, or are relatively complex toassemble. Moreover, even in fireplaces which do disassemble for transit,the combined bulk of the disassembled parts is considerable, resultingin increased shipping and storage costs. The fireplaces are relativelycomplicated to fabricate, and in most cases are not particularlyeffective as space heaters, often being more ornamental than practical.

Open fireplaces are commonly employed to burn wood, or possiblyartifical firelogs as an alternative, and the design of efficient woodburning fireplaces has presented considerable problems because of thedifficulty of obtaining complete combustion of the wood and avoidingblow backs and accumulations of "creosote" in flues and chimneys whichpresent a fire hazard. Possibly the most effective woodburning fireplaceyet devised is Benjamin Franklin's Pennsylvanian fireplace of which theinventor published an account as long ago as 1744. Unfortunately theoriginal design is difficult to fabricate economically under present dayconditions, and extensive modifications in the design which have beenmade to facilitate the production of present day "Franklin" fireplaceshave seriously reduced their effectiveness. A number of otherwoodburning fireplace designs have been evolved, but all are less thanideal in appearance and/or performance and most are unsuited to economicfabrication from sheet metal and in modern designs.

SUMMARY OF THE INVENTION

The present invention seeks to provide a fireplace which can burn woodefficiently and completely, which can be incorporated in an efffectiveheating, ventilating and air conditioning system for a room or home,which is simple to fabricate and assemble, which is of neat appearance,which is easy to operate, and which can be packed compactly for shippingor storage.

In a first aspect, the invention provides a fireplace comprising animperforate bowl shaped fire-pan having extended sloping sides tosupport fire building material, a fire enclosure superposed on an outerrim of the fire-pan, said enclosure including a generally conical hoodtapering to a flue and defining an opening above the rim of the fire-panto the exterior of the fireplace, the opening being positioned anddimensioned so that heat may be directly radiated through it from atleast the central portion of the fire-pan to a substantial part of theenvironment of the fireplace. A fire built in such a fireplaceconveniently includes a large first log laid across that sloping side ofthe fire-pan opposite the opening in the enclosure, and second and thirdsmaller logs resting at their one ends on the first log and at theirother ends on spaced locations on the sloping sides of the fire-pan toeither side of the opening so that the logs frame the central area ofthe fire-pan as seen through the opening.

Such a fireplace structure has several advantages over conventionalfireplaces in which the combustible material is either supported on agrate or placed on a flat open fronted hearth. With a grate, there is arelatively unobstructed air flow upward through the material, whichtends to burn rather rapidly, whilst ashes drop through the grate andaccumulate. With combustion on a flat hearth there is also anaccumulation of ash and it may become difficult to maintain adequatecombustion. With the bowl shaped fire-pan of the present invention, thesloping sides of the pan support the combustible material clear of thebottom of the pan and at the same time tend to direct any ash towardsthe bottom. However, it is found that the configuration of the pan alsopromotes gas flow which prevents excessive accumulations of ash, thelighter particles being entrained in the flue gases. The fireplace isthus substantially self cleaning. The bowl shape of the fire-pan alsoinhibits excess air flow past the combustible matter so that combustiontakes place more completely and at a controlled rate which can beeffectively reduced to a low rate without the fireplace structure abovethe fire-pan needing to be particularly gas tight. This controlled rateof combustion together with the configuration of the combustion chamberis also found to eliminate or greatly reduce creosote formation bycausing more complete combustion of the gaseous decomposition productsof the fuel.

The invention also extends to a fireplace comprising a fire-pan, agenerally conical fire enclosure extending upwardly from the fire-pan toa flue and having a side opening, a general frustoconical casingconcentrically surrounding the fire enclosure and having a side openingin register with the opening in the fire enclosure, and a fire doorassembly rotatably supported concentrically intermediate between theenclosure and the casing, said assembly comprising a frame havingportions projecting above and outwardly of the top of the frustoconicalcasing, a mesh screen and a door plate each supported by said frame andeach bounding sufficient of the periphery of the conical enclosure to berotatable into a position obturating the opening therein, a sufficientportion of the periphery of the enclosure being unbounded by either thescreen or the plate to permit the frame to be rotated so that at least asubstantial portion of the opening in the enclosure is unobturated.

This arrangement provides a fireplace with a particularly comprehensivemethod of controlling the fire. It is especially advantageous whenemployed with the dished grateless fire-pan referred to above with whichit enables a high degree of control to be exercised on the rate ofcombustion of the fire even though the seals between the fire doorassembly, the fire enclosure and the fire-pan are not fully airtight.

The invention further extends to a fireplace comprising an imperforatefire-pan, a fire enclosure extending upwardly from the rim of thefire-pan to a flue extending out of a room in which the fireplace isinstalled, an opening defined by the wall of the fire enclosure, anouter casing surrounding the fire enclosure and defining an aircirculation space between the casing and the enclosure extending from abottom opening from the atmosphere of the room beneath the fire-pan to atop opening to the room above the fire enclosure, said outer casinghaving an intermediate opening in register with the opening in theenclosure, and a fresh air vent extending into the bottom opening of theouter casing from outside the room, whereby air from both outside theroom and from beneath the fire-pan inside the room may convect throughthe circulation space and into the room at a higher level, and air froman intermediate level in the room may exhaust through the intermediateopening in the casing, the opening in the fire enclosure, and the flue.

By this arrangement, the fireplace may be incorporated in acomprehensive heating and ventilation system, and by the furtheraddition of a water pan beneath the fire pan the air circulating throughthe room may be conditioned by addition of humidity.

SHORT DESCRIPTION OF THE DRAWINGS

The invention is described further with reference to the accompanyingdrawings, wherein:

FIG. 1 shows a perspective view of a first embodiment of fireplace inaccordance with the invention,

FIG. 2 is a plan view of the same fireplace,

FIG. 3 is a view corresponding to FIG. 1, showing the fireplace with theaddition of an outer casing,

FIG. 4 is a vertical section through the fireplace of FIG. 3,

FIG. 5 is a vertical section through the fireplace of FIG. 3, packed fortransit,

FIG. 6 is a perspective view of a modified form of the fireplace,

FIG. 7 is an exploded perspective view of the fireplace of FIG. 6,

FIG. 8 is a vertical section through the fireplace of FIG. 6, on theline 8--8 in FIG. 7,

FIG. 9 is a vertical section through the fireplace of FIG. 6, packed fortransit,

FIGS. 10 and 11 are cross-sectional diagrams illustrating use of thefireplaces for space heating purposes.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1 to 4, a fireplace is shown which comprises abaseplate 2, an open work spacer member 4, a fire-pan 6, a hood formedby a conical enclosure 8, a fire screen 10 and, in the case of FIGS. 3and 4, a frustoconical casing 12.

The dished fire-pan 6 receives the fire directly and is flow turned fromheavy gauge sheet steel, a small central portion 13 being connected to asurrounding rim 16 by a sloping wall 14, the rim 16 being connected tothe wall 14 by an annular step 18, and being surrounded by an unturnedannular flange 20. In use, the central portion 13 and wall 14 may becovered with a layer of fire clay or equivalent refractory material 22(shown in broken lines in FIG. 10) in which case a lighter gauge ofsteel may be used for the pan. Flow turning is a metal forming processwhich differs from spinning in that only a single forming pass isinvolved, rather than the successive deformations carried out by thevarious forming passes during spinning. In flow turning, coactingforming tools are moved gradually outwards relative to a rotating metalworkpiece as the forming pass proceeds, and the forming pressures aremuch higher than those used in spinning. As compared with spinning, flowturning has the advantage of enabling much deeper conical configurationsto be formed, and also enables an unworked and undeformed flange to beleft at the external periphery of the formed workpiece. The technique offlow turning is sometimes known as shear forming or roll forming.

The base 2 is a circular disc of sheet metal with a raised centralcircular portion 24, the step between the portion 24 and the remainderof the disc serving to locate a base ring 26 of the open work spacer 4.This spacer consists of the base ring 26, a larger diameter top ring 28,and a number of rods 30 connecting the base and top rings. The spacer isfabricated from steel rod and has an inverted frusto-conicalconfiguration. The step 18 of the fire-pan 6 is located within the topring 28, thus firmly locating the fire-pan in relation to the base.Instead of providing the step 18, locating brackets may be welded to theunderside of the fire-pan, the spacer being releasably locked to the panby a snib pivotally mounted beneath the latter.

Standing on the fire-pan 6 is a fire enclosure which in this embodimentconsists solely of the cone 8. This cone is formed from sheet steel by aflow turning process, a horizontally extending flange 31 of the originalsheet being left at the bottom of the cone, this flange resting on therim 16 so as to locate the base of the cone 8 within the flange 20. Forgreater security, the cone may be releasably retained within the pan bydetents in the form of tongues punched inwardly from the flange 20 ofthe fire-pan. The apex of the cone is truncated and formed with avertical annular flange 32 with enables connection to be made to a fluepipe (not shown).

An opening 34 is cut in the wall of the cone 8, the opening being largeenough to expose the greater part of the fire-pan 6 (see FIG. 1), and toshield this opening against flying sparks when a fire is burning in thefire-pan, the fire screen 10 is provided. The fire screen 10 is ofgenerally similar shape to the opening 34, but slightly larger, andrests in the channel 38 formed between the cone 8 and the flange 20, thefire screen being movable in the channel by means of a handle 38 so asto expose a greater or lesser portion of the opening 34.

The portion of the cone 8 cut away in order to form the opening 34 iswelded within the opposite side of the cone so as to form a fire back 40which shields the cone 8 from overheating by the fire and possibledamage.

In order to increase the efficiency of the fire as a space heater, anadditional component is preferably added to the hood in the form of afrusto-conical casing 12. This is formed by flow turning in the samemanner as the cone 8, but its configuration differs slightly. The baseof the frustum is slightly wider than that of the cone and is formedwith a depending flange 42 which rests within the flange 20 and supportsthe casing so as to leave an air gap between it and the cone 8. Anannular top flange 44 is flared into the frustum and is of substantiallygreater diameter than the flange 32 so as to leave an annular air gapbetween the two flanges. Air vents 46 are formed in the rear of thecasing towards its lower end, and an opening 48 is providedcorresponding to and registerable with the opening 34.

In order to assemble the fireplace, the various components are merelystacked coaxially one upon the other. Indeed, assembly and disassemblyis so easy that the user of the fireplace may readily disassemble is formovement between different locations, for example for alternative use inan indoor location in connection with a permanently installed flue, orin an outdoor location in which it may if desired be converted into abarbecue by placing a gridiron over the fire-pan. Likewise, the ease ofassembly and disassembly allows the fireplace to be stored away duringthe summer months if desired. The structure is perfectly stable withoutthe optional snib and detents referred to previously but their presencemay be preferred for added security.

The possibilities discussed in the preceding paragraph are still furtherenhanced by the ease with which the fireplace may be packed into acompact space for transportation or storage. A section of the fireplacein its packed condition is shown in FIG. 5, in which it will be seenthat the casing 12 (if used) is inverted, the inverted cone 8 is droppedwithin the enclosure, the open work spacer 4 is dropped within the cone8, the fire-pan is placed on the flange 30 of the cone 8 so that thedished portion 14 projects within the cone, and the base 2 is invertedand placed in the fire-pan. The fire door 36 may be packed eitherbetween the cone and the casing, as shown, or within the cone 8. It willbe seen that the entire fireplace is packed form need occupy no morespace than the casing 12 alone, or the cone 8 if the casing is notprovided.

Operation of the fireplace when in use is generally conventional, exceptthat the fire is built directly in the fire-pan 6. It should be observedthat the open work spacer 4 leaves unobstructed the entire under surfaceof the fire-pan 6, thus permitting maximum emission of heat by radiationand convection from this surface. When the casing 12 is used, thefireplace becomes an even more effective space heater, with air enteringthe space between the cone 8 and the casing 12 through the gap betweenthe edges of the openings 34 and 48 and through the air vents 46, andleaving through the gap between the flanges 32 and 44. A furtheradvantage of using the casing is that since it is insulated from thecone by an air space, its temperature remains relatively low. Not onlyis this desirable from the point of view of safety, but it means thatdecorative finishes such as heat resistant paint may be applied to theouter surface of the casing 12, whereas only vitreous and otherexpensive refractory finishes would be suitable for the outer surface ofthe cone 8. The use of paint rather than a refractory finish representsan important economy in manufacture.

The fire is built so that its materials rest on the sloping wall 14 asseen in FIGS. 10 and 11, a preferred log arrangement when burning woodhas a large back log 50 resting across the back of wall 14 and twosmaller logs 52 resting on the back log and upon the front portion ofwall 14 to either side of opening 34. The sloping wall 14 tends todirect ashes downwards towards central portion 13 of the fire-pan,completing combustion of wood to fly ash, and it is found that theairflow from opening 34 through the fire-pan and the interior of theenclosure to the flue is such as to make the fire substantially selfcleaning, the fly ash being entrained and removed through the flue. Itis found that combustion of the gases from the burning wood is much morecomplete, because these gases entrain further air from opening 34 for asecondary combustion process in the enclosure above the fire. Thisincreases efficiency and reduces the possibility of creosoteaccumulation. For these advantages to be obtained the wood must beburned directly in the fire-pan without the use of a grate.

A more sophisticated embodiment of the fireplace is shown in FIGS. 6-9,in which corresponding parts have the same reference numerals increasedby the addition of 100. The baseplate 2 is replaced by a base memberwhich is an annular trough 102, and the spacer member is replaced by aninverted frusto-conical skirt 104 with a vertical bottom flange 101flared into the frustum. This flare is produced by post-flow-turningexpansion of the metal of the small end of the frustum, as is the casewith other flared components used in the fireplace. The skirt issupported from the base member by bolts 103 passing through spacerbrackets secured within the flange 101, so as to define an annularopening 107 into a space within the skirt and beneath the fire-pan 106.

The fire-pan is supported within an upper flange 109 on the skirt bymeans of bolts 111 passing through spacers 115 and a rim 116 of thefire-pan, so that a further annular opening 117 is defined between therim 116 and the flange 109. The fire-pan requires no annular stepcorresponding to the step 18 but is otherwise similar in configurationto the fire-pan 6.

The lower flange 131 of a conical enclosure 108 is also secured by thebolts 11 so as closely to surround the rim 116 of the fire-pan. Apartfrom the configuration of the flange 131, the enclosure 108 is similarto the enclosure 8, with a top flange 132 for connection to a flue pipe119, and an opening 134.

The casing 112 is substantially the same as the casing 12, but itincludes no vents corresponding to the vents 46. Instead, it rests withits lower flange 142 closely surrounding the flange 109 of the skirt sothat the annular opening 117 opens into the space 121 between the casingand the enclosure, thus defining a continuous air passage surroundingthe fire-pan 106 and enclosure 108 from the opening 107 adjacent thebottom of the skirt 104 to the opening 123 adjacent the top of thecasing 112.

The fire screen 110 forms part of a fire control assembly housed in thespace 121. The assembly comprises a tripod rod framework, with threediverging legs 127 connected by upper and lower annuli 129 and 133, thelower annulus 133 being above the level of the top of the openings 134in the enclosure 108 and 148 in the casing 112. Extending downwardlyfrom the annulus 133 between and downwardly from two of the legs 127 isthe fire screen 110, and a metal fire door 135 extends similarly betweenand downwardly from an adjacent two of the legs. The fire screen 110 isof expanded metal, oriented so that when the fireplace is viewed from infront (i.e. the side with the openings 134 and 148) and above, the meshof the expanded metal when the screen obturates the openings causesminimum obscuration of an observer's view of the fire-pan 106. The topsof the legs 127 are bent so as to extend vertically and are fitted withtubular sockets 137 to receive spokes 139 of an annular operating handle141 supported by the spokes radially outwardly of the opening 123. Theassembly is supported on the enclosure 108 by the annuli 129 and 133,its centre of gravity being such that the door 135 tends to rest againstthe enclosure.

In a preferred arrangement, the opening 141, bounded by the annulartrough member 102, is connected, as best seen in FIG. 11, to the outsideof a building in which the fireplace is installed by means of a duct 143through which air may enter the space beneath the fire-pan 106 to mixwith air entering through the opening 107. Admission of such externalair to the space is controlled by a flap valve 145 connected by a hinge147 to an inturned flange on member 102. The valve may be moved toalternative open or closed positions by means of an operating handle 149pivotally connected to a bracket 151 on the valve, which handle may bemanually hooked over alternative brackets 153 and 154 on the outermargin of member 102 to define the open and closed positions. The valveis hinged at its front edge so as to direct the main incoming airflowrearwardly away from the opening 134.

The trough member 102 may be filled with water through a filler pipe 155mounted on the skirt 104, by means of a funnel inserted into the top endof the pipe between the bottom edges of the openings 134 and 148. Adip-stick (not shown) may be provided to gauge the water level in thetrough member, and may include a cap to close the top of the pipe.

As in the case of the previous embodiment, many of the components may beflow turned, thus producing seamless components of superior quality atmoderate cost.

Referring to FIG. 9, it will be seen that the various components may bepacked for transit in a similar manner to that described for the firstembodiment with respect to FIG. 5. Indeed, in spite of the greatercomplexity of the fireplace structure, it occupies no more space whenpacked and will in fact fit in boxes originally designed to accommodatethe embodiments of FIGS. 1-5.

The fireplace of FIGS. 6-9 may be operated as already described withreference to FIG. 10, but further features of its operation will beapparent from FIG. 11. It will be seen that, when the flap valve 145 isopen, air from the duct 143 will enter the space between the fire-pan106 and blend with air entering from the room in which the stove islocated through the opening 107, whence under the influence of heattransmitted to it from the fire-pan 106 and the enclosure 108 it willconvect upwardly through the opening 126 and then circulate around theroom as indicated by the arrows before re-entering the opening 107.Stale air from the central area of the room will pass through theopenings 134 and 148 to provide combustion air for the fire, and will beexhausted up the flue. The recirculating air will be humidified bypicking up moisture evaporated from the water in the trough member 102,evaporation being assisted by the heat radiated downwardly by thefire-pan 106. There will be some admixture of air around the edges ofthe openings 134 and 148, but this will not significantly affect theoperation.

The fire may be controlled by rotating the assembly 125. The assemblymay be moved to a first, normal position, in which the screen 110 isframed in the openings 134 and 148 and forms a fireguard, or so thatneither the screen 110 nor the door 135 appears in the openings so thefire may be stoked. When it is desired to reduce the rate of combustion,as for overnight operation, the door is moved into the opening so thatair flow into the enclosure is reduced to a low level. Since with thepresent fireplace only a relatively small proportion of the air enteringthe enclosure actually passes through the fire, much greater leakage canoccur than would be permissible with conventional stoves which can beclosed for overnight burning. Leakage around the door will be reduced inany event since the position of the centre of gravity of the assembly125 will tend to bias the door into contact with the enclosure 106. Bymoving the door so that it renders the opening 134 relatively narrow. itmay be used to induce an accelerated draught when a fire is being lit.Because the operating handle 141 is radially outward of the opening 123it does not become uncomfortably hot whilst being accessible and easy tooperate.

What I claim is:
 1. A fireplace comprising a fire-pan, a generally conical fire enclosure extending upwardly from the fire-pan to a flue and having a side opening, a generally frusto-conical casing concentrically surrounding the fire enclosure and having a side opening in register with the opening in the fire enclosure, and a fire door assembly rotatably supported concentricallly intermediate between the enclosure and the casing, said assembly comprising a frame having portions projecting above and outwardly of the top of the frusto-conical casing, a mesh screen and a fire door plate each supported by said frame and each bounding sufficient of the periphery of the conical enclosure to be rotatable into a position obturating the opening therein, a sufficient portion of the periphery of the enclosure being unbounded by either the screen or the door plate to permit the frame to be rotated so that at least a substantial portion of the opening in the enclosure is unobturated.
 2. A fireplace according to claim 1 in which the projecting portions of the frame include an annular handle concentric with the flue.
 3. A fireplace according to claim 1 in which the screen is of expanded metal mesh, with the mesh openings oriented so as to provide maximum visibility of the fire through the screen from above and in front of the fireplace when the screen obturates the opening in the enclosure.
 4. A fireplace according to claim 1 in which the weight of the fire door assembly is distributed relative to its points of support on the enclosure so as to bias the door plate towards the enclosure. 